This invention relates to a motorized trailer maneuvering jack having a compact power drive wheel.
The need to maneuver a conventional trailer while uncoupled from its tow vehicle (to aid in coupling, uncoupling, or general maneuvering) is well known in the art. Various maneuvering jack drives for conventional trailers have been proposed.
U.S. Pat. No.3,783,960 describes one such trailer maneuvering jack. The device described in this patent is quite bulky, complex, and expensive to build. The bulkiness of this design affects the operation of the trailer in several ways, including extra tongue weight, setback of the drive assembly in the tongue A-frame which in some cases interferes with trailer payload, rotational interference of the drive motor and/or wheel with the tongue when maneuvering the trailer with the tongue lowered, and undesirable twist or side torque when used with a straight tongue.
U.S. Pat. No.3,861,482 describes another such trailer maneuvering device. This device is also quite bulky which, if used in a tongue A-frame, does not allow it to be mounted as far forward as is desirable. Also, with a straight tongue, the offset mounting will impart undesirable twist or torque.
U.S. Pat. No.4,860,841 describes still another such device for maneuvering a trailer. In a first embodiment described in this patent the described device employs two ground contacting wheels attached to the jack which makes it hard to steer since one wheel will slide if the direction of travel is changed. Also, the device is mechanically complex which increases cost. The second embodiment of this patent shows one wheel set to the side of a tongue jack end, which causes torque around the tongue jack centerline and urges the tongue jack to rotate in circles. The offset power wheel also limits compactness and interferes with tongue clearance, especially when fully retracted.
It is an object of this invention to provide a simple, compact, and easily maneuverable power driven wheel assembly for a trailer jack.
It is a further object to provide an assembly that will nest forward into the tongue A-frame to increase payload space and provide more ground clearance while still being able to rotate 360 degrees.
It is a still further object to provide a drive head that can be fully retracted at an angle without contacting the tongue.
It is a another object to provide a drive head that will reduce or eliminate tongue twist around the tongue centerline when mounted on a straight tongue trailer.
The trailer maneuvering jack of the invention has a compact drive wheel attached to the extendable inner sleeve or rod of a tongue jack in such a manner that it is located along the longitudinal axis of the tongue jack, the axle of the wheel being perpendicular to the longitudinal axis of the tongue jack.
The tongue jack is preferably comprised of a cylindrical outer sleeve and a cylindrical inner sleeve or rod located within the outer sleeve, the inner sleeve or rod having a longitudinal axis coaxial with the longitudinal axis of the outer sleeve. However, the inner and outer sleeves may be non-cylindrical.
A power drive mounting bracket is attached at its upper end to the lower end of the inner sleeve or rod, the lower end of the bracket being attached to a drive wheel assembly comprised of a motor, drive train, and wheel. The centerline of the motor is located at the wheel axle centerline.
In a first embodiment the case of the motor is cylindrical and constitutes the axle of the wheel, the wheel being mounted thereon by wheel bearing means. The drive shaft of the motor is operably connected to the wheel by a drive train. The drive train is comprised of the drive shaft of the motor the outer end of which constitutes a pinion gear that drives a planetary gear set that meshes with and drives a rotational ring gear. A drive sleeve attached to the wheel bearing is driven by the rotational ring gear.
In a second embodiment of the invention the rotational ring gear forms the axle of the wheel.